Could an o2 sensor cause this?

[kastein]

Sounds like a fuse for the O2 heater could make a pretty decent "first mod" on a new Renix XJ then.

 

[collkid]

There, fixed it.

I'll give 'er a shot tomorrow, if it's still where I left it.

Thanks

:compwork:
haha how funny.

 

[SteveT]

OK, snuck out on lunch to have another try. Cables were thoroughly inspected for crud, and are (now) immaculate. Bolt on terminal out, scrubbed inside and out, and coated with with acid neutralizer, wire brushed, sprayed with protectant, and reinstalled.

Now, just dealing with that Fuse #20, 30amp. Didn't bring the test lamp, so I chose to sacrifice fuses.

Cable "upgrade", new fuse, key to on, fuse blows.

Pull ASD relay, new fuse, key to on, fuse OK

Swap ASD with A/C relay, key to on, fuse blows.

New fuse, disco rear O2 sensor, key on fuse blows, out of time, go back to work.


Am I heading in the right direction? I'll go for the front O2 sensor next. How could I test the injectors for a short? I can disco the alt, and try things again, but how would I test the coil? Do I just pull the lead (to the dist), or should I pull the power before the coil?

At least the snow stopped.

Steve

 

[JJacobs]

All the wires in the affected circuit are the same color. I would disconnect everything in my list that runs off that fuse all at the same time. Then turn the key on, another blown fuse equals wiring fault.

 

[gradon]

Repeat your process w/ the front o2, then the cps, then tb sensors, then injectors, etc. When you repaired the wires, did you inspect them down the line from the break to see if any copper is bare?

 

[JJacobs]

Repeat your process w/ the front o2, then the cps, then tb sensors, then injectors, etc. When you repaired the wires, did you inspect them down the line from the break to see if any copper is bare?

Now why would you want to go unplugging things that aren't on the affected circuit? Circuit A142, dark green/ orange tracer is the problem child, not the vref for tps, map, iac, ckp etc. A142 feeds the injectors, alternator, ignition coil, o2 heaters only.

 

[SteveT]

Gradon - old O2 was sensor was replaced last year. It started throwing a code, and it was e-test time, so I replaced.

New discoveries today: Front O2 doesn't seem to be problem. Disco'd and still pops fuse.

Pulled power lead to coil, still popped.

If I turn key to on and leave it, I can put a new fuse in, and it won't pop. If I crank engine, it pops.

Key off, no voltage passes through fuse sockets. Key to on, and 11.8v (basically battery voltage, as it's getting a little tired, but that's what battery tested to) hits fuse socket, but for only a second or so, then drops to 0.0v.

More laying in the slush underneath revealed the two wires from my tranny (AX-15), which I assume to be for reverse lights, touched exhaust and melted one side of male plug (part of the harness, not the switch).

On the surface, this doesn't seem to be part of the equation, but it is very new damage (as in just happened), and that wiring enters into the harness, which then runs forward towards the coil, and the coil is in the affected loop.

I hope to get it towed home tomorrow, and not have to worry about it being left in public. My wifes work schedule, and Halloween activities cut into my time.

Any further thoughts are appreciated.

Steve

 

[SteveT]

Some shots of what I found:

 

[SteveT]

Steve, F20 powers the ASD relay. You could remove the relay and see if it still blows the fuse, if so it is something downstream of the relay shorted whether wire or component. The ASD relay powers the injectors, the 02 heaters, ignition coil and alternator. Disconnect components one at a time to find the short. To save on fuses rig a test light into the fuse socket, if it glows as brightly as when hooked across the battery there is a short present.

All the wires in the affected circuit are the same color. I would disconnect everything in my list that runs off that fuse all at the same time. Then turn the key on, another blown fuse equals wiring fault.

New discoveries today: Front O2 doesn't seem to be problem. Disco'd and still pops fuse.

Pulled power lead to coil, still popped.

If I turn key to on and leave it, I can put a new fuse in, and it won't pop. If I crank engine, it pops.

Key off, no voltage passes through fuse sockets. Key to on, and 11.8v (basically battery voltage, as it's getting a little tired, but that's what battery tested to) hits fuse socket, but for only a second or so, then drops to 0.0v.

More laying in the slush underneath revealed the two wires from my tranny (AX-15), which I assume to be for reverse lights, touched exhaust and melted one side of male plug (part of the harness, not the switch).

On the surface, this doesn't seem to be part of the equation, but it is very new damage (as in just happened), and that wiring enters into the harness, which then runs forward towards the coil, and the coil is in the affected loop.

Alrighty then, I'm once again mobile, thanks to JJacobs:cheers:

The quotes above are what I was trying to do, I just wasn't sure if I was doing it right. Jon graciously gave me a few hours this morning, and it was a productive exercise in the process of elimination. He has some extra gear that eased the process (and saved fuses), and I'm a little smarter (that ain't hard to do).

It turned out that the melted wiring for the reverse lights was a non-issue. I'm not a fan of coincidence, but that may be just what it was. We couldn't make the connection (no pun intended) with that, and the affected circuit.

The FSM was great for getting things sorted out. Get one if you can. It showed all the systems that Jon had spelled out, that were affected by the ASD relay, and the fuse that was blowing. One by one we (uh, he, cough cough) eliminated all components on that circuit, and still couldn't keep it from popping. That lead to the suppostion of bad wiring.

Jon has a gizmo (pretty sure that's what it's called) that you can plug into the end of a circuit, and it will generate a "tone" that is transmitted through the wiring. There's also a wireless receiver that you can run along the harness to pinpoint the damaged/shorted area. It'll even indicate which direction you should go if you come to a bundle that "T's" in different directions.

Signs pointed to a short in the injector loom. The wiring was crusty, but intact, and showed no signs of shorts. I was about ready to start slitting apart the loom, when Jon wiggled the loom downstream of the injectors, and the tone of the gizmo changed to a solid note, and helped to isolate this...

That's the upstream side of the front O2 sensor wiring. It was routed poorly, and too close to the header. It never actually burned through, and the damage was concealed. Years of heat had crispied the insulation on the four wires, and eventually they shorted.

So even though the component was good, and the wiring up to the plug in the harness was good, the damage lay hidden up inside the split plastic loom.

A little electrical tape for a temp repair, a little code clearing with a pro scanner, and we's rockin.

Off to the yard tomorrow to snag some uncrispy harness, and a little splicing and I'll be (um, the Jeep will be) 100%...Once I put my new sticker on.

Props to Jacobs :worship:

 

[JJacobs]

Glad we got it working! Yeah, it was probably electrical tool overkill but I wanted to try some of the new goodies. It would have been a quicker fix but I learned something after it threw me for a loop: I did not know the ASD relay acted like the fuel pump relay, only energized for a couple seconds and then back off until cps rpm input detected. Learn something every day. :thumbup: Now back on the trails you go.

 

[Tim_MN]

Details on the nifty diagnostic tool ? Brand, model, where to find one ?

 

[Ecomike]

Interesting sounding gismo. Details?

Sounds like a cool way avoid tearing up wire looms in the search for shorts.

I think the wiring on the O2 sensor wires is where I suggested looking for bad insulation and a short earlier in this thread, but perhaps I was not clear enough?

 

[JJacobs]

Interesting sounding gismo. Details?

Sounds like a cool way avoid tearing up wire looms in the search for shorts.

I think the wiring on the O2 sensor wires is where I suggested looking for bad insulation and a short earlier in this thread, but perhaps I was not clear enough?

Even a blind squirrel finds a nut once in a while. j/k. That's the thing about shorts, they're always plain as day once found but without any visible external harness damage that can be a chore. The shortfinder is ok, it could be a little more accurate. It really shines when looking for shorted taillight wiring or similar that could be almost anywhere in the whole vehicle.

This is it: http://www.etooldirect.com/power-probe-model-ect2000-wireless-short-finder.html

 

[SteveT]

:thumbup: Now back on the trails you go.

Yeah the trails...or maybe the mall, like Mason, to die.

p.s. I forgot to mention I made Jon babysit my kids and load a minivan while he was on call. - membership has its privileges

 

[Ecomike]

Thanks, I will check it out.

Oh, and I don't know that I have ever run across a blind squirrel before, LOL.Besides, I think they smell the nuts out, LOL.

Even a blind squirrel finds a nut once in a while. j/k. That's the thing about shorts, they're always plain as day once found but without any visible external harness damage that can be a chore. The shortfinder is ok, it could be a little more accurate. It really shines when looking for shorted taillight wiring or similar that could be almost anywhere in the whole vehicle.

This is it: http://www.etooldirect.com/power-probe-model-ect2000-wireless-short-finder.html

 

[joe_peters]

Thanks, I will check it out.

Oh, and I don't know that I have ever run across a blind squirrel before, LOL.Besides, I think they smell the nuts out, LOL.

Well, even after you have run across them, you should still be able to see the little white cane in the road.:roflmao: